THE BONES, PART 1 - PRESERVATION, AGE & ORIGIN

Preservation the bones recovered from Mineral Hill Cave are exceptionally well preserved. The temperature of the cave is a near-constant 40 degrees with greater than 90% humidity. These bones have essentially sat in a refrigerator for thousands of years. The BLM is currently working with Paleoscience, Inc. of Miami, Florida to determine if paleoDNA is preserved in these bones. More information on extracting paleoDNA from ancient bone specimens is available at www.paleoscience.com.

Age

The BLM has contracted with Stafford Research Labs of Boulder, Colorado, and Beta Analytic of Miami, Florida to radiocarbon date individual bone specimens from Mineral Hill Cave. The BLM obtained 55 Accelerator Mass Spectrometry (AMS) dates on 52 different bone specimens recovered throughout the cave. These dates range from 2,000 years ago to >50,000 years ago. Radiocarbon dating is currently accurate to about 45,000 to 50,000 years ago. Specimens that return dates that are older than 50,000 years are considered "infinite", meaning that we know the specimen is at least 50,000 years old, but we don’t know how much older. Many of the bones date between 30,000 and 45,000 years ago, indicating that this was a relatively active time of bone deposition in the cave.

Bones that are 40,000 years old were found next to bones that are only 8,000 years old, confirming the mixing that has occurred to the deposits, probably by the burrowing activities of marmots. The BLM also submitted a series of charcoal samples from Test Pit 1. Charcoal dated to 600 years ago was found over one meter deep in association with bones that dated to 30,000 years ago, confirming McGuire’s earlier interpretation that the deposits had been thoroughly churned in the past.

Origin

Many of the bones recovered from Mineral Hill Cave were carried into the site by carnivores. Three pieces of evidence support this interpretation. First, a number of subadult carnivore mandibles were found in Chamber 5, most notably young bobcat mandibles. Carnivore remains in general are relatively common. Rich numbers of carnivore bones, and especially the presence of subadult carnivore remains, generally indicates carnivore denning in caves. Second, the vast majority of large mammal bones are represented by lower leg and foot bones. This bone patterning is typically seen in assemblages in which carnivores scavenge large mammal cacasses and carry the lower limbs and feet to a den site. Third, hundreds of small and large mammal, as well as bird bones, exhibit carnivore tooth punctures, and hundreds of large mammal limb bone shaft fragments were recovered. These latter bones were produced by carnivores chewing and splitting long bones in order to eat the marrow inside the shafts of these bones.

These latter bones were produced by carnivores chewing and splitting long bones in order to eat the marrow inside the shafts of these bones.

The Mineral Hill Cave collection also contains hundreds of intact bones of smaller animals such as bats, lizards, mice, woodrats, and marmots which may have simply died naturally inside the cave.